Method of removing particles and a liquid from a surface of substrate

ABSTRACT

The present invention is related to a method of removing particles and a liquid from a surface of a substrate using at least one rotating cleaning pad. The approach, according to the present invention, is a technique wherein a sharp liquid-vapor boundary is created on the surface of the substrate adjacent to the last wetted rotating cleaning pad of a plurality of rotating cleaning pads and particularly between this last wetted rotating cleaning pad and a first edge of the substrate.

[0001] This application claims priority benefits under 35 U.S.C. § 119to United States provisional application Ser. No. 60/059,929, filed onSep. 24, 1997, and to United States provisional application Ser. No.60/066,164, filed on Nov. 19, 1997.

FIELD OF THE INVENTION

[0002] The present invention is related to a method of cleaning andremoving a liquid from a surface of a substrate by means of a rotatingcleaning pad. Said method can be used in the fabrication process ofintegrated circuits, especially when the preceding processing step hasheavily contaminated the surface.

BACKGROUND OF THE INVENTION

[0003] In general, the complete and efficient removal of a liquid from asurface of a substrate is a multiply repeated step in e.g. thefabrication process of integrated circuits. Such a step can be performedafter a wet etching step or a wet cleaning step or a wet rinsing step orany other step used in said fabrication process wherein said substrateis treated or exposed or immersed in a liquid. Said substrate can be asemiconductor wafer or a part thereof or a glass slice or any otherslice of an insulating or conductive material.

[0004] The manufacturing of integrated circuits evolves towardsprocessing of each substrate individually rather than in batches ofseveral substrates. In the state of the art of IC manufacturing, mostprocessing steps, such as implantation steps, deposition steps, arealready performed in a single substrate mode. On the other hand, wetprocessing steps, such as cleaning steps and subsequent liquid removalsteps, are typically performed in a batch mode because of a lack ofappropriate alternatives. Therefore, differences in waiting times arecreated for each individual substrate between a wet processing step,performed in a batch mode and another processing step, performed in asingle substrate mode. Such variability is undesirable with regard toprocess control. Moreover this mixed batch and single substrateprocessing increases the cycle time, which is also undesirable.Therefore, there is a general interest in the development of competitivesingle substrate wet processing steps. Particularly, one of the majorchallenges regarding single wafer wet processing is a method forremoving a liquid from both sides of a substrate. There are two majorrequirements to be fulfilled for such a method. First, it should worksufficiently fast. In state of the art production lines, a substrate isprocessed typically every 2 to 3 minutes. Ideally, in order to avoidequipment duplication, the liquid removal should be completed in aboutsuch a time frame. Another requirement is related to the preferredorientation of the substrate. State of the art processing equipment andtransportation tools are developed to handle substrates in a horizontalposition. Therefore in order to avoid additional substrate handling, itwould be desirable to perform the wet processing steps usinghorizontally positioned substrates.

[0005] In the European Patent EP 0 385 536 B1, a method is disclosed ofdrying substrates after treatment in a liquid by pulling said substrateslowly out of said liquid. However, to be effective, this known method,which is based on the Marangoni principle, requires that the substratesare pulled out of the liquid in an upright position, i.e. a surface ofsaid substrate is about perpendicular to the surface of the liquid bath(as can be seen in FIGS. 1 to 6 of the European Patent EP 0 385 536 B1).This handling is incompatible with the majority of the other processsteps where the equipment and transportation tools are developed tohandle horizontal positioned substrates.

[0006] In the U.S. Pat. No. 5,271,774, a spin-drying technique isdisclosed which is able to handle horizontal positioned substrates. Infact, several small liquid islands are formed being removed from thesubstrate by a rotary movement. It is known that such a spin-dryingtechnique leaves undesirable residues, often referred to as dryingmarks, on the substrate surface, particularly on surfaces having mixedhydrophilic and hydrophobic regions. Furthermore, this technique is notsuited to remove residual contamination in the form of particles.

[0007] It is clear from the above discussion that there is a generalinterest in single wafer wet processing and drying. Therefore, anefficient drying technique which also has good cleaning capabilities isa prerequisite. For some inherently dirty processes such as chemicalmechanical polishing, cleaning steps making use of a mechanical forceare used nowadays. For instance, CMP machines typically used forplanarizing or smoothing a semiconductor wafer surface employ a polishslurry containing generally sub-micron sized abrasive particles of amaterial such as silica or alumina. Large quantities of such particles,along with particles removed from the wafer itself during the polishingoperation, may be found on a polished wafer surface. These particlesmust be removed in a cleaning step or they may drastically affect deviceyield.

[0008] For instance, in the U.S. Pat. No. 5,581,837, disk-shapedobjects, e.g. wafers, are transported one at the time between a set ofrotating brushes so as to be cleaned thereby. In fact, in the presenceof a cleaning liquid, a mechanical force is exerted on the surface ofthe wafer by means of the rotating brushes to get the wafers cleaned.This cleaning step can be followed subsequently by a rinsing step and aseparate drying step. In this drying step, IR lamps are used toperforming the drying. It is known that such a technique leaves dryingmarks on the surface of the substrate.

SUMMARY OF THE INVENTION

[0009] In an aspect of the invention, a method for removing ofcontamination particles and a liquid from a surface of a substrate usingat least one rotating cleaning pad is disclosed. This rotary cleaningpad is preferably cylindrical shaped and has an outer edge which cancontact a surface of a substrate. Particularly, a method is disclosedfor the removal of particles and a liquid from at least one surface of asubstrate using a plurality of rotating cleaning pads comprising thesteps of:

[0010] creating a relative linear motion at a predetermined speedbetween a plurality of wetted rotating cleaning pads and a substrate;

[0011] contacting said surface of said substrate at a first edge witheach of the wetted rotating cleaning pads of said plurality of wettedrotating cleaning pads each time that during said relative linear motionsaid wetted rotating cleaning pad arrives at said first edge;

[0012] applying a gaseous substance on said surface adjacent to a lastwetted rotating cleaning pad, being the last wetted rotating cleaningpad of said plurality of rotating cleaning pads arriving at said firstedge, and between said last wetted rotating cleaning pad and said firstedge, said gaseous substance being at least partially miscible with saidliquid and when mixed with said liquid yielding a mixture having asurface tension being lower than that of said liquid; and

[0013] continuing said linear relative motion from said first edge to asecond edge, opposite to said first edge, while contacting said surfaceof said substrate with said plurality of wetted rotating cleaning padsand while supplying said gaseous substance to thereby remove saidparticles and said liquid from said surface of said substrate. Saidgaseous substance can comprise a vaporised substance which is misciblewith said liquid and when mixed with said liquid yields a mixture havinga surface tension being lower than that of said liquid. A vaporisedsubstance is defined as a mist of finely dispersed liquid droplets of anelement or a compound or a mixture of elements or as a vapor. A vapor isdefined as the gas phase occurrence of an element or of a compound or ofa mixture of elements if the element or compound or mixture should be inthe liquid or solid phase at the given temperature and pressureconditions. Thus a vapor can co-exist in one environment with the solidor liquid phase of the element. A vapor is a specific gas phaseoccurrence of an element or a compound or a mixture of elements. Saidgaseous substance can comprise a gas which is miscible with said liquidand when mixed with said liquid yields a mixture having a surfacetension being lower than that of said liquid. Said gaseous substance cancomprise a mixture of a vaporised substance and a gas, particularly aninert gas like e.g. helium, argon or nitrogen, said mixture being atleast partially miscible with said liquid and when mixed with saidliquid yielding a mixture having a surface tension being lower than thatof said liquid. In an embodiment of the invention, said cleaning pad ismoved relative to said substrate while wetting said rotating cleaningpad by supplying liquid to said rotating pad or to said first portion ofsaid surface adjacent to said rotating cleaning pad.

[0014] The approach, according to the present invention, is a techniquewherein a very sharp liquid-vapor boundary is created on said surface ofsaid substrate adjacent to said last rotating cleaning pad between saidlast wetted rotating cleaning pad and said first edge.

[0015] The relative linear motion can be created in an arbitrarydirection including a vertical motion or an horizontal motion. Thesubstrates and/or the cleaning pads can be advanced. Particularly, atransportation belt can be used to advance the substrates.

[0016] In another embodiment of the invention, the rotary cleaning padand particularly the last rotating cleaning pad is cylindrical shapedand has an outer edge which can contact a surface of a substrate.Preferably this outer edge of the cleaning pads is wider than the widthof the area of the surface in contact with the cleaning pad. In otherwords, when contacting said surface, at least a part of the outer edgeof the cleaning pad extends beyond the edges of the substrate.Preferably, the rotating cleaning pad is selected such that when wet andwhen a predetermined pressure is exerted on said cleaning pad acontinuous contact area is created between the cleaning pad and thesurface of the substrate. More preferably said rotary cleaning pad has apolymeric smooth outer edge. The pad may further comprise a layerunderlying said polymeric outer edge, said layer being more compressiblethan said polymeric outer edge.

[0017] In another embodiment of the invention, a method is disclosed forcleaning and removing a liquid from a surface of a substrate using apair of rotating cleaning pads. Said rotating cleaning pads are arrangedin parallel and spaced apart one above the other. A first rotatingcleaning pad is used for contacting a first surface of the substrate, asecond cleaning pad is used for contacting a second surface of saidsubstrate opposite to said first surface. The rotating cleaning pads andthe substrate are handled such that a substrate can be advanced at anadjustable speed through said pair of rotating pads from said first edgeof said substrate to said second edge of said substrate, said secondedge being opposite to said first edge. Alternatively, the rotatingcleaning pads and the substrate can be handled such that said pair ofrotating cleaning pads can be advanced at an adjustable speed from saidfirst edge of said substrate to said second edge of said substrate, saidsecond edge being opposite to said first edge.

[0018] In another embodiment of the invention, two sets of rotatingcleaning pads can be used for removing particles and a liquid from asurface of a substrate. A first set of rotating cleaning pads is usedfor contacting a first surface of the substrate, said first setcomprising a first plurality of wetted rotating cleaning pads, a secondset of rotating cleaning pads is used for contacting a second surface ofsaid substrate opposite to said first surface, said second setcomprising a second plurality of wetted rotating cleaning pads. Therotating cleaning pads within each set are parallel to and spaced apartone from the other, while each rotating cleaning pad of the first set isspaced apart from and face in face to a rotating cleaning pad of thesecond set one above the other. In the latter case a gaseous substanceis only supplied after and adjacent to the last rotating cleaning pad ateach surface to thereby clean and dry said surface.

[0019] In another aspect of the invention, a method is disclosed for theremoval of particles and a liquid from at least one surface of asubstrate using a plurality of rotating cleaning pads comprising thesteps of:

[0020] creating a relative linear motion at a predetermined speedbetween a plurality of wetted rotating cleaning pads and a substrate;

[0021] contacting said surface of said substrate at a first edge witheach of the wetted rotating cleaning pads of said plurality of wettedrotating cleaning pads each time that during said relative linear motionsaid wetted rotating cleaning pad arrives at said first edge;

[0022] locally heating said liquid on said surface adjacent to a lastwetted rotating cleaning pad, being the last wetted rotating cleaningpad of said plurality of rotating cleaning pads arriving at said firstedge, and between said last wetted rotating cleaning pad and said firstedge, to thereby locally reduce the surface tension of said liquid; and

[0023] continuing said linear relative motion from said first edge to asecond edge of said substrate, opposite to said first edge, whilecontacting said surface of said substrate with said plurality of wettedrotating cleaning pads and while locally heating said liquid to therebyremove said particles and said liquid from said surface of saidsubstrate. To initiate the drying process, the liquid is locally heatedby a heat source to reduce the surface tension to thereby create asharply defined liquid-ambient boundary on said surface of saidsubstrate adjacent to said last rotating cleaning pad between said lastwetted rotating cleaning pad and said first edge. Particularly, the heatsource can be a nozzle, movable or not, or a static inlet dispensing aheated gas or a heated vapor or a heated mixture of a vapor and a gas.But also other heat sources can be used such as laser beams or otherenergetic beams, provided that they can be sufficiently localized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 represents a schematic cross-section of a wet processingtool, according to an embodiment of the invention, wherein a substrateis advanced through two revolving scrubbers to thereby clean and drysaid substrate.

[0025] In FIG. 1a, the rotating cleaning pads (2) contact the substrate(1) at a first edge (7).

[0026] In FIG. 1b, the substrate is advanced partly through the rotatingcleaning pads.

[0027] In FIG. 1c, the substrate is advanced completely through therotating cleaning pads.

[0028]FIG. 2 represents a schematic cross-section of a wet processingtool, according to an embodiment of the invention, wherein two revolvingcleaning pads are advanced across a fixed substrate to thereby clean anddry said substrate.

[0029] As illustrated in FIG. 2, a substrate (1) is placed between twomovable revolving cleaning pads (4). A first movable arm (5), is placedclose to the first rotating cleaning pad at the top side of thesubstrate while a second movable arm (5) is placed close to a secondcleaning pad at the bottom side of said substrate. The arms comprise atleast one nozzle (6) for supplying a surface tension reducing vapor tothe substrate. In FIG. 2a, both wetted rotating cleaning pads and botharms are positioned at an edge of the substrate and the vapor issupplied at a first side of both rotating cleaning pads. In FIG. 2b, thearms and the cleaning pads are moved simultaneously over the surfaces ofthe substrate in the direction of second edge (8). In FIG. 2c, theopposite edge (8) is reached, the entire substrate is cleaned and dried.

[0030]FIG. 3 represents a schematic cross-section of a wet processingtool, according to an embodiment of the invention wherein the to andbottom side of a substrate are each contacted with a plurality ofrotating cleaning pads.

DETAILED DESCRIPTION OF THE INVENTION

[0031] In relation to the appended drawings the present invention isdescribed in detail in the sequel. Several embodiments are disclosed. Itis apparent however that a person skilled in the art can imagine severalother equivalent embodiments or other ways of executing the presentinvention, the spirit and, scope of the present invention being limitedonly by the terms of the appended claims.

[0032] In an embodiment of the invention a method of removing particlesand a liquid from a surface of a substrate using at least one rotatingcleaning pad is disclosed. The approach, according to the presentinvention, is a technique wherein a sharp liquid-vapor boundary iscreated on said surface of said substrate adjacent to said last wettedrotating cleaning pad between said last wetted rotating cleaning pad andsaid first edge of said substrate. The configuration is such that theliquid is kept at the portion of the surface to be cleaned adjacent tosaid rotating cleaning pad contacting the surface. A gaseous substanceis supplied adjacent to and at the other side of the rotating pad on theportion of said surface which is already cleaned. Said gaseous substanceis at least partially miscible with said liquid and when mixed with saidliquid results in a surface tension reduction of said liquid therebyenhancing the movement of said liquid towards the rotating cleaning pad.The part of the surface left behind, i.e. said second portion is cleanedand dried. It is presumed that the cleaning of said surface resultspartly from the frictional cleaning of a rotating cleaning padcontacting the substrate. This frictional cleaning performance can becontrolled by adjusting the rotational speed of the cleaning pad, byadjusting the speed of the relative movement of the substrate to thecleaning pad and by adjusting the pressure at which the rotatingcleaning pad is pressed on the surface of the substrate. Particularly ifthe rotating cleaning pad is brought in contact with a surface of thesubstrate at a predetermined pressure and no extra force would beexerted either on said cleaning pad or on said substrate, the substratewould be advanced solely due to the rotary motion of said cleaning pad.In such a case, the cleaning pad would hardly exert a frictional forceon said surface. If, for instance, the speed of the relative motion ofthe cleaning pad to the substrate is controlled, then this speed can beadjusted, e.g. be lowered or reversed, in order to increase thefrictional force of the rotating cleaning pad on the surface to therebyenhance the cleaning performance, i.e. the removal of particles. Thisfrictional cleaning forms the mechanical component of the cleaningaction, while by the selection of the liquid also a chemical cleaningcomponent can be introduced. Besides the removal of the particles alsothe liquid is removed. It is presumed that this drying action isobtained due the combination of at least the chemical and mechanicalcomponent of the cleaning action and the Marangoni effect. According tothis effect, said gaseous substances will be at least partially mixedwith the liquid such that in the liquid meniscus, its concentrationdecreases in the direction of the liquid. This gradient in concentrationcreates an additional force exerted on the liquid film in the directionof the liquid film, resulting in a good drying performance. Moreover,also the cleaning performance can be enhanced due to the Marangonieffect and especially by the creation of a liquid-vapor boundary.

[0033] The liquid is selected dependent upon the preceding processingstep and particularly the degree of contamination present on a surfaceof the substrate. A cleaning liquid or a rinsing liquid can be used. Toinitiate the drying process, a gaseous substance reducing the surfacetension of said liquid is dispensed on at least one surface of saidsubstrate. Particularly, a pressurized gaseous substance is activelysupplied e.g. by using at least one inlet, said inlet preferably beingmovable and comprising at least one nozzle. More particularly arectangular nozzle can be used, parallel to said rotating cleaning pad,for dispensing said gaseous substance on said second portion of saidsurface, said nozzle having a very limited width, i.e. typically in therange from 0.1 to 10 mm and an extended length being parallel to therotary axis of the rotating cleaning pad, i.e. at least as long as themaximum width of the substrate. The length from such a line-shapednozzle can be typically in the range from 10 to 30 cm. Instead of oneline-shaped nozzle, a plurality of small circular nozzles can beprovided along the rotary axis of the cleaning pad. Particularly, saidsurface tension reducing gaseous substance can be isopropyl alcohol(IPA).

[0034] The rotary cleaning pads are preferably cylindrical shaped andhave an outer edge which can contact a surface of a substrate. Alsoscrubbers and brushes can be used as cleaning pads. More preferably, therotating cleaning pad and especially the last rotating cleaning pad isselected such that when wet and when a predetermined pressure is exertedon said cleaning pad a continuous contact area is created between thecleaning pad and the surface of the substrate. Even more preferably,said rotary cleaning pad has a polymeric smooth outer edge. The pad mayfurther comprise a layer underlying said polymeric outer edge, saidlayer being more compressible than said polymeric outer edge.Particularly, before contacting a surface of the substrate liquid issupplied on the rotating cleaning pads to wet these cleaning pads. Then,when contacting the surface of the substrate with the rotating cleaningpads, the liquid is transferred to the surface. The cleaning pads cancomprise means for supplying additional liquid to thereby wet saidcleaning pads and eventually a part of the surface which still is to becleaned. Alternatively liquid can also be dispensed on said cleaningpads and/or on the part of the surface which still is to be cleaned.Preferably no additional liquid is supplied to or adjacent to the lastrotating cleaning pad.

[0035] The liquid is chosen dependent upon the degree of contaminationpresent on a surface of the substrate. In case a cleaning liquid isused, preferably a mixture of NH₄OH, H₂O₂ and H₂O; or a mixture ofdilute NH₄OH, and H₂O; or a mixture of HCl, H₂O₂ and H₂O; or dilute HClis used. In case a rinsing liquid is used, preferably H₂O or anycombination of H₂O and an acid having a pH between 2 and 6 is used.

[0036] Said gaseous substance can comprise a vaporised substance whichis miscible with said liquid and when mixed with said liquid yields amixture having a surface tension being lower than that of said liquid. Avaporised substance is defined as a mist of finely dispersed liquiddroplets of an element or a compound or a mixture of elements or as avapor. A vapor is defined as the gas phase occurrence of an element orof a compound or of a mixture of elements if the element or compound ormixture should be in the liquid or solid phase at the given temperatureand pressure conditions. Thus, a vapor can co-exist in one environmentwith the solid or liquid phase of the element. A vapor is a specific gasphase occurrence of an element or a compound or a mixture of elements.Said gaseous substance can comprise a gas which is miscible with saidliquid and when mixed with said liquid yields a mixture having a surfacetension being lower than that of said liquid. Said gaseous substance cancomprise a mixture of a vaporised substance and a gas, like e.g. helium,argon or nitrogen, said mixture being at least partially miscible withsaid liquid and when mixed with said liquid yielding a mixture having asurface tension being lower than that of said liquid. Preferably, saidvaporised substance is isopropyl alcohol (IPA), but also several othervaporised substances like e.g. diacetone, ethylglycol, methylpyrrolidoncan be used.

[0037] In a preferred embodiment of the invention, as illustrated inFIG. 1, a method is disclosed for removing particles and a liquid from asurface of a substrate using a pair of rotating cleaning pads. Saidrotating cleaning pads are arranged in parallel and spaced apart, oneabove the other. A first rotating cleaning pad is used for contacting afirst surface of the substrate, a second cleaning pad is used forcontacting a second surface of said substrate opposite to said firstsurface. Particularly, a substrate (1) is placed between two revolvingcleaning pads (2), said cleaning pads having a length at least as longas the length or diameter of said substrate. The substrate is preferablya thin slice or piece of material like e.g. a semiconductor wafer or aglass plate or a metal plate. A first arm (3), is placed close to saidfirst cleaning pad at the top side of the substrate while a second arm(3) is placed close to the second cleaning pad at the bottom side ofsaid substrate. Furthermore these arms comprise at least one nozzle (6),preferably line-shaped, for supplying a surface tension reducing vaporto both surfaces of the substrate. According to the method of thepresent invention, initially both wetted rotating cleaning pads eachcontact a surface of the substrate at a first edge (7) of the substrate(FIG. 1a). Then, the substrate is moved through the pair of rotatingcleaning pads from said first edge to a second edge (8), opposite tosaid first edge while supplying a gaseous substance adjacent to eachrevolving pad at the portion of each surface which is located betweensaid first edge and the rotating cleaning pad (in other words, the partof the surface which is already cleaned). By doing so on both surfacesof the substrate, a liquid-vapor boundary is formed which is initiallylocated at said first edge of said substrate. Then said substrate isadvanced (FIG. 1b) through said cleaning pad to thereby guide saidboundary slowly outwards from said first edge of the substrate to theopposite second edge of said substrate while removing the liquid (9) orthe solution of said liquid from said surfaces of said substrate. Whensaid opposite second edge is reached (FIG. 1c), the entire substrate ismoved through the rotating cleaning pads thereby yielding a cleaned anddried substrate. Particularly, the wetted rotating cleaning pads can bebrought in contact with the substrate while exerting a predeterminedadjustable pressure on said cleaning pads. Both cleaning pads rotate inopposite directions, which would result in a linear movement of thesubstrate in a first direction at a speed dependent on the rotationspeed of the cleaning pads if this movement would not be controlled.However, by controlling this linear movement, the frictional force ofthe rotating cleaning pads on the surfaces is controlled, therebyenhancing the cleaning performance. Particularly, the speed can belowered or preferably even reversed which results in a linear movementin a second direction opposite to said first direction. For instance,when using cleaning pads with a diameter ranging from 1 to 6 cm, thetypical rotation speed can be in the range from 0.1 to 10 rotations persecond while the linear translation speed ranges typically from 1 to 10mm per second. Note that diameter ranges and rotation speed may bechosen based on user need, so that the invention is not limited tospecific diameter ranges or rotation speeds. Furthermore, the rotationalspeed of the cleaning pads is chosen in a manner that splashing of theliquid on the part of a surface, which is already cleaned and dried, isprevented.

[0038] Alternatively, as illustrated in FIG. 2, a pair of movablecleaning pads (4) can be used. These movable rotating cleaning pads andthe substrate can be handled such that said pair of movable rotatingcleaning pads can be advanced in a linear movement at an adjustablespeed from a first edge (7) of said substrate to a second edge (8) ofsaid substrate, said second edge being opposite to said first edge. Inparticular, in FIG. 2a, both wetted rotating cleaning pads and both armsare positioned at an edge of the substrate and the vapor is supplied ata first side of both rotating cleaning pads. In FIG. 2b, the arms andthe cleaning pads are moved simultaneously over the surfaces of thesubstrate in the direction of second edge (8). In FIG. 2c, the oppositeedge (8) is reached, the entire substrate is cleaned and dried.

[0039] In an alternate preferred embodiment of the invention (FIG. 3), amethod is disclosed for the removal of particles and a liquid from afirst and a second surface of a substrate using a first and a secondplurality of rotating cleaning pads. Particularly, said first and secondsurface can be the top and bottom surface of a substrate. This methodcomprises the steps of:

[0040] a) creating a relative linear motion at a predetermined speedbetween both said first and said second plurality of wetted rotatingcleaning pads and said substrate;

[0041] Preferably, the first plurality of wetted rotating cleaning padsand the second plurality of wetted rotating cleaning pads are movedsimultaneously. The rotating cleaning pads within each plurality ofwetted rotating cleaning pads are parallel to and spaced apart one fromthe other, while each rotating cleaning pad of said first plurality isspaced apart from and face in face to a rotating cleaning pad of saidsecond plurality one above the other.

[0042] b) contacting said first surface of said substrate at a firstedge with each of the wetted rotating cleaning pads of said firstplurality of wetted rotating cleaning pads and said second surface ofsaid substrate at said first edge with each of the wetted rotatingcleaning pads of said second plurality of wetted rotating cleaning pads,said contacting being established each time that during said relativelinear motion said wetted rotating cleaning pad arrives at said firstedge;

[0043] c) applying a gaseous substance on said first surface adjacent toa first last wetted rotating cleaning pad, being the last wettedrotating cleaning pad of said first plurality of rotating cleaning padsarriving at said first edge, and between said first last wetted rotatingcleaning pad and said first edge, said gaseous substance being at leastpartially miscible with said liquid and when mixed with said liquidyielding a mixture having a surface tension being lower than that ofsaid liquid;

[0044] d) applying a gaseous substance on said second surface adjacentto a second last wetted rotating cleaning pad, being the last wettedrotating cleaning pad of said second plurality of rotating cleaning padsarriving at said first edge, and between said second last wettedrotating cleaning pad and said first edge, said gaseous substance beingat least partially miscible with said liquid and when mixed with saidliquid yielding a mixture having a surface tension being lower than thatof said liquid;

[0045] Preferably said gaseous substance is supplied simultaneous tosaid first and second surface of said substrate.

[0046] e) continuing said linear relative motion from said first edge toa second edge, opposite to said first edge, while contacting said firstsurface of said substrate with said first plurality of wetted rotatingcleaning pads and said second surface of said substrate with said secondplurality of wetted rotating cleaning pads and while supplying saidgaseous substance to said first and second surface to thereby removesaid particles and said liquid from said first and second surface ofsaid substrate.

What is claimed is:
 1. A method for the removal of particles and liquidfrom at least one surface of a substrate using a plurality of rotatingcleaning pads comprising the steps of: creating a relative linear motionat a predetermined speed between the plurality of wetted rotatingcleaning pads and the substrate; contacting said surface of saidsubstrate at a first edge with each of the wetted rotating cleaning padsof said plurality of wetted rotating cleaning pads each time that duringsaid relative linear motion said wetted rotating cleaning pad arrives atsaid first edge; applying a gaseous substance on said surface adjacentto a last wetted rotating cleaning pad, being the last wetted rotatingcleaning pad of said plurality of rotating cleaning pads arriving atsaid first edge, and between said last wetted rotating cleaning pad andsaid first edge, said gaseous substance being at least partiallymiscible with said liquid and when mixed with said liquid yielding amixture having a surface tension being lower than that of said liquid;and continuing said linear relative motion from said first edge to asecond edge, opposite to said first edge, while contacting said surfaceof said substrate with said plurality of wetted rotating cleaning padsand while supplying said gaseous substance to thereby remove saidparticles and said liquid from said surface of said substrate.
 2. Amethod as recited in claim 1 , wherein by supplying *said gaseoussubstance, a sharply defined liquid-vapor boundary is created on saidsurface of said substrate adjacent to said last rotating cleaning padbetween said last wetted rotating cleaning pad and said first edge.
 3. Amethod as recited in claim 1 , wherein during said relative linearmotion, liquid is supplied to at least one of said plurality of wettedrotating cleaning pads contacting said surface of said substrate.
 4. Amethod as recited in claim 1 , wherein said liquid is selected from agroup consisting of a mixture of NH₄OH, H₂O₂ and H₂O; a mixture ofdilute NH₄OH, and H₂O; a mixture of HCl, H₂O₂ and H₂O; dilute HCl; H₂O;and a mixture of H₂O and an acid, said mixture having a pH between 2 and6.
 5. A method as recited in claim 1 , wherein said gaseous substancecomprises a vaporised substance which is miscible with said liquid andwhen mixed with said liquid yields a mixture having a surface tensionbeing lower than that of said liquid.
 6. A method as recited in claim 5, wherein said vaporised substance is selected from a group consistingof isopropyl alcohol (IPA), diacetone, ethylglycol, ethyllactate andmethylpyrrolidon or a mixture thereof.
 7. A method as recited in claim 1, wherein said gaseous substance comprises a mixture of a vaporisedsubstance and a gas, said mixture being at least partially miscible withsaid liquid and when mixed with said liquid yields a mixture having asurface tension being lower than that of said liquid.
 8. A method asrecited in claim 7 , wherein said vaporised substance is selected from agroup consisting of isopropyl alcohol (IPA), diacetone, ethylglycol andmethylpyrrolidon or a mixture thereof and wherein said gas is an inertgas.
 9. A method as recited in claim 1 , wherein said gaseous substancecomprises a gas which is miscible with said liquid and when mixed withsaid liquid yields a mixture having a surface tension being lower thanthat of said liquid.
 10. A method as recited in claim 1 , wherein saidlast rotating cleaning pad is cylindrical shaped and has a smooth outeredge.
 11. A method as recited in claim 1 , wherein a continuous contactarea is formed between said last rotating cleaning pad and said surface.12. A method as recited in claim 1 , wherein said plurality of wettedrotating cleaning pads consists of a single rotating cleaning pad.
 13. Amethod for the removal of particles and a liquid from a first and asecond surface of a substrate using a first and a second plurality ofrotating cleaning pads comprising the steps of: creating a relativelinear motion at a predetermined speed between both said first and saidsecond plurality of wetted rotating cleaning pads and said substrate;contacting said first surface of said substrate at a first edge witheach of the wetted rotating cleaning pads of said first plurality ofwetted rotating cleaning pads and said second surface of said substrateat said first edge with each of the wetted rotating cleaning pads ofsaid second plurality of wetted rotating cleaning pads, said contactingbeing established each time that during said relative linear motion saidwetted rotating cleaning pad arrives at said first edge; applying agaseous substance on said first surface adjacent to a first last wettedrotating cleaning pad, being the last wetted rotating cleaning pad ofsaid first plurality of rotating cleaning pads arriving at said firstedge, and between said first last wetted rotating cleaning pad and saidfirst edge, said gaseous substance being at least partially misciblewith said liquid and when mixed with said liquid yielding a mixturehaving a surface tension being lower than that of said liquid; applyinga gaseous substance on said second surface adjacent to a second lastwetted rotating cleaning pad, being the last wetted rotating cleaningpad of said second plurality of rotating cleaning pads arriving at saidfirst edge, and between said second last wetted rotating cleaning padand said first edge, said gaseous substance being at least partiallymiscible with said liquid and when mixed with said liquid yielding amixture having a surface tension being lower than that of said liquid;continuing said linear relative motion from said first edge to a secondedge, opposite to said first edge, while contacting said first surfaceof said substrate with said first plurality of wetted rotating cleaningpads and said second surface of said substrate with said secondplurality of wetted rotating cleaning pads and while supplying saidgaseous substance to said first and second surface to thereby removesaid particles and said liquid from said first and second surface ofsaid substrate.
 14. A method for the removal of particles and a liquidfrom at least one surface of a substrate using a plurality of rotatingcleaning pads comprising the steps of: creating a relative linear motionat a predetermined speed between a plurality of wetted rotating cleaningpads and a substrate; contacting said surface of said substrate at afirst edge with each of the wetted rotating cleaning pads of saidplurality of wetted rotating cleaning pads each time that during saidrelative linear motion said wetted rotating cleaning pad arrives at saidfirst edge; locally heating said liquid on said surface adjacent to alast wetted rotating cleaning pad, being the last wetted rotatingcleaning pad of said plurality of rotating cleaning pads arriving atsaid first edge, and between said last wetted rotating cleaning pad andsaid first edge, to thereby locally reduce the surface tension of saidliquid; and continuing said linear relative motion from said first edgeto a second edge of said substrate, opposite to said first edge, whilecontacting said surface of said substrate with said plurality of wettedrotating cleaning pads and while locally heating said liquid to therebyremove said particles and said liquid from said surface of saidsubstrate.
 15. A method as recited in claim 14 , wherein by locallyheating said liquid, a sharply defined liquid-ambient boundary iscreated on said surface of said substrate adjacent to said last rotatingcleaning pad between said last wetted rotating cleaning pad and saidfirst edge.
 16. A method as recited in claim 14 , wherein said heatingis accomplished by means of dispensing a gas or a vapor or a mixture ofa gas and a vapor.
 17. A method as recited in claim 14 , wherein saidheating is accomplished by means of irradiation with an energetic beam.